Obesity is a major public health problem in this country. Currently the mechanisms which underlie the development of obesity are obscure. While a complex interaction between nutrient intake, energy expenditure and fuel metabolism exists, evidence in humans and laboratory animals suggests that abnormal partitioning of triglyceride fatty acids (TGFA) favoring storage over oxidation may play a central role in the development of some forms of obesity. it is hypothesized that defects in the oxidation and storage of lipid fuel within skeletal muscle play an important role in the development and maintenance of the obese state by shunting dietary fat towards storage in adipose tissue. The goal of the research projects proposed is to test this hypothesis by following the metabolic fate of lipid fuels in skeletal muscle from lean and obese rats. In addition the enzyme systems responsible for the metabolism of fatty acids within skeletal muscle will be examined in detail. Over the last 20 years radioactive tracer studies have shed important new light on the abnormalities of carbohydrate metabolism which are present in obesity and type II diabetes. Studies of TGFA metabolism however have lagged far behind, and yet may provide important insights into the mechanisms which underlie the development and maintenance of obesity.